Session: 112. Thalassemia and Globin Gene Regulation: Poster III
Hematology Disease Topics & Pathways:
sickle cell disease, Biological, Diseases, thalassemia, Therapies, Hemoglobinopathies, Biological Processes, gene therapy, Technology and Procedures, gene editing, Clinically relevant
Results. Here we tested HSC mobilization by truncated MGTA-145, a CXCR2 agonist, and plerixafor in the context of in vivo HSC transduction. CD46-transgenic animals were mobilized with GCSF + plerixafor (5 days) or with MGTA-145 + plerixafor (same-day treatment) and then injected one hour later with an integrating HDAd5/35++ mgmt/GFP vector. MGTA-145 + plerixafor resulted in robust mobilization of HSCs, less leukocytosis and no significant elevation of cytokines, as observed with G-CSF + plerixafor. With both mobilization regimens, after in vivo selection with O6BG/BCNU, >90% of PBMCs expressed GFP and marking rates were stable long-term. Mice were sacrificed 12 weeks after in vivo transduction and bone marrow lineage-negative cells were harvested for transplantation into secondary recipients. Stable transgene expression (>90% at week 16 after transplantation) was observed with both mobilization regimen in secondary recipients and multilineage engraftment was observed with MGTA-145 + plerixafor in primary and secondary recipients.
Importantly, the mobilization with MGTA-145 + plerixafor worked efficiently in a mouse disease model for thalassemia (Hbbth3/CD46+/+). In this model, after in vivo transduction with an integrating HDAd5/35++mgmt/gamma-globin vector and in vivo selection, over 95% of peripheral red blood cells (RBCs) expressed human gamma-globin. The gamma-globin protein level reached 36% over mouse beta-globin. Phenotypic analyses showed a complete correction reflected by normal RBC morphology and absence of blood reticulocytosis, extramedullary hemopoiesis and hemosiderin deposition in spleen and liver sections. In secondary recipients of Lin- cells (harvested at week 14 from in vivo transduced Hbbth3/CD46+/+ mice), gamma-globin marking in RBCs was stable at 99% (currently at week 11 after transplantation). This demonstrates that MGTA145 + plerixafor mobilizes long-term repopulating HSCs.
Conclusions. These data demonstrate that the combination of MGTA-145 and plerixafor could serve as an efficient and potentially safer one-day mobilization regimen for in vivo HSC gene therapy in patients with hemoglobinopathies.
Disclosures: Goncalves: Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Davis: Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Kiem: Rocket Pharma: Membership on an entity's Board of Directors or advisory committees; Umoja: Membership on an entity's Board of Directors or advisory committees; CSL: Consultancy; Homology Medicines: Membership on an entity's Board of Directors or advisory committees; Vor Biopharma: Membership on an entity's Board of Directors or advisory committees; Enochian: Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy. Lieber: Ensoma, Inc: Consultancy, Research Funding.
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